Nuclear Theory·nucl-th

Friday·October 12, 2018

12 papers—6 primary·6 cross-listed

01
[Submitted on 10 Oct 2018]
Non-local interactions in the $(d, p)$ surrogate method for $(n, γ)$ reactions
Weichuan Li · Gregory Potel · Filomena Nunes
Single-neutron transfer reactions populating states in the continuum are interesting both for structure and astrophysics. In their description often global optical potentials are used for the nucleon-target interactions, and these interactions are typically local. In our work, we study the effects of nonlocality in $(d, p)$ reactions populating continuum states. This work is similar to that of [1] but now for transfer to the continuum. A theory for computing cross sections for inclusive processes $A (d, p) X$ was explored in [2]. Therein, local optical potentials were used to describe the nucleon-target effective interaction. The goal of the present work is to extend the theory developed in [2] to investigate the effects of including nonlocality in the effective interaction on the relevant reaction observables. We implement the R--matrix method to solve the non--local equations both for the nucleon wavefunctions and the propagator. We then apply the method to systematically study the inclusive process of $(d, p)$ on $^{16}$ O, $^{40}$ Ca, $^{48}$ Ca and $^{208}$ Pb at 10, 20 and 50 MeV. We compare the results obtained when non--local interactions are used with those obtained when local equivalent interactions are included. We find that nonlocality affects different pieces of the model in complex ways. Depending on the beam energy and the target, the non-elastic breakup can either increase or decrease. While the non-elastic transfer cross section for each final spin state can change considerably, the main prediction of the model [2], namely the shape of the spin distributions, remains largely unaltered by nonlocality. [1] L. J. Titus and F. M. Nunes. Testing the Perey effect. Phys. Rev. C, 89:034609, Mar 2014. [2] G. Potel, F. M. Nunes, and I. J. Thompson. Establishing a theory for deuteron-induced surrogate reactions. Phys. Rev. C, 92:034611, Sep 2015.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.04751 [pdf]
PRC(2018)·12 citations
02
[Submitted on 10 Oct 2018]
Blind spots of probing the high-density symmetry energy in heavy-ion collisions
Gao-Chan Yong🇨🇳
The nuclear symmetry energy, especially at suprasaturation densities, plays crucial roles in many astrophysical studies. However, nowadays the high-density behavior of the symmetry energy is still very controversial in nuclear community. To constrain the high-density behavior of the symmetry energy, neutron-rich nuclei collisions at medium energies are considered to be one of the most effective methods. While probing the high-density symmetry energy by using heavy-ion collisions, blind spots may exist. In the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, the blind spots of probing the high-density symmetry energy by the n/p ratio in the central Au+Au reaction at 300 MeV/nucleon are demonstrated. It is found that the nucleon observable neutron to proton ratio n/p in heavy-ion collisions cannot effectively probe the high-density symmetry energy when the high-density symmetry energy is less density-dependent.
Comments:
5 pages, 3 figures, accepted by PLB
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1810.04787 [pdf]
PLB(2018)·5 citations
03
[Submitted on 11 Oct 2018]
In-medium properties of a $Ξ N$ interaction derived from chiral effective field theory
J. Haidenbauer🇩🇪 · U.-G. Meißner🇩🇪
The in-medium properties of a baryon-baryon interaction for the strangeness $S = - 2$ sector derived within chiral effective field theory up to next-to-leading order are investigated. The considered $Ξ N$ interaction is in line with available empirical constraints on the $ΛΛ$ $S$ -wave scattering length and on $Ξ N$ elastic and inelastic cross sections. In particular, there are no near-threshold bound states in the $Ξ N$ system. A conventional $G$ -matrix calculation for this interaction is performed and reveals that the single-particle potential of the $Ξ$ -hyperon in nuclear matter is moderately attractive as suggested by recent experimental evidence for the existence of $Ξ$ -hypernuclei.
Comments:
9 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.04883 [pdf]
EPJA(2019)·60 citations
04
[Submitted on 11 Oct 2018]
Phase structure of neutron $^{3} P_{2}$ superfluids in strong magnetic fields in neutron stars
Shigehiro Yasui🇯🇵 · Chandrasekhar Chatterjee🇯🇵 · Muneto Nitta🇯🇵
We discuss the effect of a strong magnetic field on neutron $^{3} P_{2}$ superfluidity. Based on the attraction in the $^{3} P_{2}$ pair of two neutrons, we derive the Ginzburg-Landau equation in the path-integral formalism by adopting the bosonization technique and leave the next-to-leading order in the expansion of the magnetic field $B$ . We determine the $(T, B)$ phase diagram with temperature $T$ , comprising three phases: the uniaxial nematic (UN) phase for $B = 0$ , D $_{2}$ -biaxial nematic (BN) and D $_{4}$ -BN phases in finite $B$ and strong $B$ such as magnetars, respectively, where D $_{2}$ and D $_{4}$ are dihedral groups. We find that, compared with the leading order in the magnetic field known before, the region of the D $_{2}$ -BN phase in the $(T, B)$ plane is extended by the effect of the next-to-leading-order terms of the magnetic field. We also present the thermodynamic properties, such as heat capacities and spin susceptibility, and find that the spin susceptibility exhibits anisotropies in the UN, D $_{2}$ -BN, and D $_{4}$ -BN phases. This information will be useful to understand the internal structures of magnetars.
Comments:
11 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Superconductivity (cond-mat.supr-con); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1810.04901 [pdf]
PRC(2019)·21 citations
05
[Submitted on 11 Oct 2018]
Two-phonon structures for beta-decay theory
A. P. Severyukhin · N. N. Arsenyev · I. N. Borzov · R. G. Nazmitdinov · S. Åberg
The $β$ -decay rates of $^{60}$ Ca have been studied within a microscopic model, which is based on the Skyrme interaction T45 to construct single-particle and phonon spaces. We observe a redistribution of the Gamow-Teller strength due to the phonon-phonon coupling, considered in the model. For $^{60}$ Sc, the spin-parity of the ground state is found to be $1^{+}$ . We predict that the half-life of $^{60}$ Ca is 0.3 ms, while the total probability of the $β x n$ emission is 6.1%. Additionally, the random matrix theory has been applied to analyse the statistical properties of the $1^{+}$ spectrum populated in the $β$ -decay to elucidate the obtained results.
Comments:
4 pages, 1 figure, proceedings of International Conference on Nuclear Structure and Related Topics (NSRT18), June 3-9 2018, Burgas, Bulgaria
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1810.04932 [pdf]
EPJ Web Conf.(2018)·0 citations
06
[Submitted on 11 Oct 2018]
Determination of the photodisintegration reaction rates involving charged particles: systematical calculations and proposed measurements based on Extreme Light Infrastructure - Nuclear Physics (ELI-NP)
H.Y. Lan · Y. Xu · W. Luo · D.L. Balabanski · S. Goriely · M. La Cognata · C. Matei · A. Anzalone · S. Chesnevskaya · G.L. Guardo · D. Lattuada · R.G. Pizzone and 5 other authors
Photodisintegration reaction rates involving charged particles are of relevance to the p-process nucleosynthesis that aims at explaining the production of the stable neutron-deficient nuclides heavier than iron. In this study, the cross sections and astrophysical rates of (g,p) and (g,a) reactions for about 3000 target nuclei with 10<Z<100 ranging from stable to proton dripline nuclei are computed. To study the sensitivity of the calculations to the optical model potentials (OMPs), both the phenomenological Woods-Saxon and the microscopic folding OMPs are taken into account. The systematic comparisons show that the reaction rates, especially for the (g,a) reaction, are dramatically influenced by the OMPs. Thus the better determination of the OMP is crucial to reduce the uncertainties of the photodisintegration reaction rates involving charged particles. Meanwhile, a gamma-beam facility at ELI-NP is being developed, which will open new opportunities to experimentally study the photodisintegration reactions of astrophysics interest. Considering both the important reactions identified by the nucleosynthesis studies and the purpose of complementing the experimental results for the reactions involving p-nuclei, the measurements of six (g,p) and eight (g,a) reactions based on the gamma-beam facility at ELI-NP and the ELISSA detector for the charged particles detection are proposed, and the GEANT4 simulations are correspondingly performed. The minimum required energies of the gamma-beam to measure these reactions are estimated. It is shown that the direct measurements of these photonuclear reactions within the Gamow windows at T_9=2.5 for p-process are fairly feasible and promising at ELI-NP. The expected experimental results will be used to constrain the OMPs of the charged particles, which can eventually reduce the uncertainties of the reaction rates for the p-process nucleosynthesis.
Comments:
14 pages, 8 figures, Phys. Rev. C accepted
Subjects:
Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
arXiv:
1810.04958 [pdf]
PRC(2018)·15 citations
07
[Submitted on 21 Jun 2018] (cross-list from hep-ph)
Decay rate and asymmetries of $Σ^{+} \to p μ^{+} μ^{-}$
Xiao-Gang He🇹🇼 · Jusak Tandean🇹🇼 · German Valencia🇦🇺
The LHCb Collaboration has recently reported evidence for the rare hyperon decay $Σ^{+} \to p μ^{+} μ^{-}$ that is consistent with the standard model expectation. Motivated by this new result we revisit the calculation of this mode including both long and short distance contributions. In the standard model this mode is completely dominated by long distance physics and thus subject to large uncertainties. We present a range of predictions for the rate, the dimuon invariant mass spectrum, and a muon polarization asymmetry that covers these uncertainties as well as known constraints. We study the interplay between short and long distance contributions which could result in additional asymmetries, but we find that they are negligible within the standard model. We propose a parameterization of these asymmetries in terms of a couple of constants that can arise from new physics.
Comments:
18 pages, 4 figures, somewhat expanded, remarks on e+e- mode & references added, matches publication
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
1806.08350 [pdf]
JHEP(2018)·29 citations
08
[Submitted on 10 Oct 2018] (cross-list from hep-ph)
Strangeness Enhancement due to String Fluctuations
H.J. Pirner🇩🇪 · B.Z. Kopeliovich🇨🇱 · K. Reygers🇩🇪
We study string fragmentation in high multiplicity proton-proton collisions in a model where the string tension fluctuates. These fluctuations produce exponential pion spectra which are fitted to the transverse momentum distributions of charged particles for different multiplicities. For each multiplicity the so obtained hadronic slope parameter defines the magnitude of the string fluctuations which in turn determines the produced ratio of strange to light quarks. PYTHIA string decay simulations are used to convert each ratio of strange to light quarks to the appropriate ratio of strange hadrons to pions.
Comments:
7 pages, 7 figures, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1810.04736 [pdf]
PRD(2020)·7 citations
09
[Submitted on 10 Oct 2018] (cross-list from nucl-ex)
Precise measurement of $α_{K}$ and $α_{T}$ for the 39.8-keV $E$ 3 transition in $^{103}$ Rh: Test of internal-conversion theory
N. Nica · J.C. Hardy · V.E. Iacob · V. Horvat · H.I. Park · T.A. Werke · K.J. Glennon · C.M. Folden III · V.I. Sabla · J.B. Bryant · X.K. James · M.B. Trzhaskovskaya
Neutron-activated sources of $^{103}$ Ru and $^{103}$ Pd both share the isomeric first-excited state in $^{103}$ Rh as a daughter product. From independent measurements of both decays, we have measured the $K$ -shell and total internal conversion coefficients, $α_{K}$ and $α_{T}$ , for the 39.8-keV $E$ 3 transition, which de-excites that state in $^{103}$ Rh, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$ -shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$ . Calculations that include the atomic vacancy indicate that the transition actually has a small $M$ 4 component with mixing ratio $δ$ = 0.023(5).
Comments:
12 pages, 6 figures. arXiv admin note: text overlap with arXiv:1704.03074, arXiv:1702.07668
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1810.04802 [pdf]
PRC(2018)·3 citations
10
[Submitted on 11 Oct 2018] (cross-list from hep-lat)
Nucleon Transversity Distribution at the Physical Pion Mass from Lattice QCD
Yu-Sheng Liu🇨🇳 · Jiunn-Wei Chen🇹🇼 · Luchang Jin🇺🇸 · Ruizi Li🇺🇸 · Huey-Wen Lin🇺🇸 · Yi-Bo Yang🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸
We report a state-of-the-art lattice calculation of the isovector quark transversity distribution of the proton at the physical pion mass. Within the framework of large-momentum effective theory (LaMET), we compute the transversity quasi-distributions using clover valence fermions on 2+1+1-flavor (up/down, strange, charm) HISQ-lattice configurations with boosted proton momenta as large as 3.0~GeV. The relevant lattice matrix elements are nonperturbatively renormalized in regularization-independent momentum-subtraction (RI/MOM) scheme and systematically matched to the physical transversity distribution. With high statistics, large proton momenta and meticulous control of excited-state contamination, we provide the best theoretical prediction for the large- $x$ isovector quark transversity distribution, with better precision than the most recent global analyses of experimental data. Our result also shows that the sea quark asymmetry in the proton transversity distribution is consistent with zero, which has been assumed in all current global analyses.
Comments:
10 pages, 4 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1810.05043 [pdf]
82 citations
11
[Submitted on 11 Oct 2018] (cross-list from hep-ph)
Effects of nucleon resonances on $η$ photoproduction off the neutron reexamined
Jung-Min Suh🇰🇷 · Sang-Ho Kim🇰🇷 · Hyun-Chul Kim🇰🇷
We investigate $η$ photoproduction off the neutron target, i.e., $γ n \to η n$ , employing an effective Lagrangian method combining with a Regge approach. As a background, we consider nucleon exchange in the $s$ -channel diagram and $ρ$ - and $ω$ -meson Regge trajectories in the $t$ channel. The role of nucleon resonances given in the Review of Particle Data Group in the range of $W \approx 1500 - 2100$ MeV and the narrow nucleon resonance $N (1685, 1/ 2^{+})$ is extensively studied. The numerical results of the total and differential cross sections, double polarization observable $E$ , and helicity-dependent cross sections $σ_{1/2}$ , $σ_{3/2}$ are found to be in qualitative agreement with the recent A2 experimental data. The predictions of the beam asymmetry are also given.
Comments:
12 pages, 6 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1810.05056 [pdf]
PRD(2019)·11 citations
12
[Submitted on 11 Oct 2018] (cross-list from hep-ph)
Initial-state energy loss in cold QCD matter and the Drell-Yan process
François Arleo🇫🇷 · Charles-Joseph Naïm🇫🇷 · Stephane Platchkov🇫🇷
The effects of parton energy loss in nuclear matter on the Drell-Yan process in pA and $π$ A collisions at fixed-target energies are investigated. Calculations are based on the Baier-Dokshitzer-Mueller-Peigné-Schiff (BDMPS) framework embedded in a next-to-leading order calculation, using the transport coefficient extracted from $J / ψ$ measurements. Model calculations prove in good agreement with preliminary measurements by the E906 experiment, despite a slightly different magnitude, supporting a consistent picture between Drell-Yan and $J / ψ$ data. Predictions for the COMPASS future measurements in $π$ A collisions at $s = 18.9$ ~GeV are also performed. At higher collision energy ( $s = 38.7$ ~GeV), Drell-Yan measurements are only slightly affected by energy loss effects. On the contrary, the E906 results turn out in clear disagreement with nuclear PDF effects alone. The comparison of E772, E866, and E906 measurements indicates for the first time a clear violation of QCD factorization in Drell-Yan production in pA collisions.
Comments:
20 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1810.05120 [pdf]
JHEP(2019)·24 citations

Affiliations

first authorsco-authorsvia INSPIRE